1. Field of the Invention
This invention relates, generally, to mitering tools. More particularly, it relates to improved means for measuring and sawing miter cuts.
2. Description of the Prior Art
The arts of carpentry, metal working, and related fields often require the craftsman to measure existing exterior and interior angles so that boards, pipes, and the like can be cut to the same angles. After a measurement has been taken, a mitering saw is used to duplicate said angles.
The process is problematic when walls, pipes, or the like converge at angles other than ninety degrees, or where walls, for example, converge at differing angles along their respective extents. For example, a pair of walls may converge at eighty eight and one half degrees at a ceiling, ninety and one third degrees midway between ceiling and floor, and ninety one and two thirds degrees at the floor. These varying angles must be accurately and quickly measured, and the measurement must then be accurately and quickly transferred to a mitering saw. Accordingly, several inventors have developed devices for measuring such angles, and for transferring the measured angles to a mitering saw so that said angles can be duplicated.
For example, U.S. Pat. No. 678,005 to Myers discloses an elongate arm having a longitudinally extending slot formed therein, and a pivot member is slidably disposed within said slot and slidable along the extent thereof. A pair of rules are pivotally mounted to the leading end of the elongate arm, and a pair of pivotally connected rods interconnect the rules and the pivot member. Thus, as the angle between the rules is changed, the pivot member slides along its slot; when a measurement is to be taken, the rules are placed against the walls the angle formed by which is to be measured, and the pivot member is locked into position. The tool is then transferred to the workpiece and the measurement is transferred thereto. Thus, the angle defined by the walls will be accurately captured, but error may be introduced when the measurement is transferred to the workpiece. More particularly, the measurement is transferred by marking the board to be cut with a pencil, and then the cut must be made along the pencil line. The pencil line itself may not accurately reflect the true position of the rules, and the cut along said line may introduce still further error because the operator of the miter saw must visually guide the saw along the pencil line.
Another device, quite similar in structure and operation to the Myers device, and subject to the same limitations, is disclosed in U.S. Pat. No. 963,274 to Bundy.
U.S. Pat. No. 3,844,043 to Gustafson also discloses a tool for gauging either internal or external angles, and transferring the angle to building material; the structure and operation thereof is very similar to that of the Myers tool. A slide means is slidable along the extent of a slide arm, lockable at any position along the extent thereof, and a pair of gauge arms are pivotally connected to the leading end of said slide arm. A pair of link members interconnect the slide arm and the gauge arms, and all of the members are connected to one another at pivot points. Thus, when the gauge arms are employed to measure an exterior angle, the slide member slides forwardly along the slide arm, and is locked into place when the gauge arms overlie the walls forming the exterior angle. When an interior angle is gauged, the slide member slides in an opposite direction, and the links pull the gauge arms into a swept wing configuration. This design has two noteworthy drawbacks; first, the link members and gauge arms must be coplanar, so the slide arm must be disposed at a different angle. Since the slide member must engage both the slide arm and the link members, the stress introduced into the device by the divergence of the link arms and the slide arm may cause jamming. Secondly, no suggestion is made as to how to transfer the measured angle to a mitering saw. Instead, the suggestion is made that the measurement be transferred directly to a building material. The mitering saw is therefore set to cut along the line transferred to the building material, and said setting may differ from the actual measured angle.
A device that overcomes both of those problems is disclosed in U.S. Pat. No. 3,709,266 to Fusco. However, that device has limitations not found in the Myers and Gustafson devices. To eliminate the problem of transferring a measurement from a measuring tool to a workpiece, the Fusco measurement tool incorporates the structure of a miter saw holder. Instead of a slide member slidably mounted to a slide arm, the slide arm itself is displaced. More particularly, the slide arm is carried on an elongate screw, and longitudinal displacement of the screw and hence of the slide arm is accomplished by rotation of a crank handle that effects simultaneous and corresponding rotation of the screw. The gauge arms are pivotally mounted to the leading end of the slide arm and the mechanism, accordingly, operates much like the Gustafson device. Although the jamming and transfer problems are eliminated, the bulk of the Fusco device, since it incorporates the miter saw holder, is considerable. Moreover, its mechanical complexity ensures that its price would easily exceed that of the Gustafson device.
A device very reminiscent of the Myers and Gustafson devices is shown in U.S. Pat. No. 4,527,341 to Schon. Like Myers and Gustafson, it is a mechanically simple parallelogram device for measuring angles. Thus, it requires the craftsman to transfer the measured angle to the workpiece, and to visually guide the mitering saw along a pencil line.
U.S. Pat. No. 5,117,560 to Nevins discloses a full circle protractor for measuring angles. It enables a craftsman to set the miter angle setting of a miter saw, and thus overcomes the limitations of those devices that require the craftsman to transfer the measurement to the workpiece with a pencil and to made a cut along the pencil line. However, the individual must still read the angle setting from the device, and then set the meter saw to that angle. Thus, the actual angle is not transferred directly to the saw; error may be introduced when the angle is read and when the angle setting is applied to the saw.
What is needed, then, is a device that eliminates the step of transferring a measured angle to a workpiece by means of a pencil or the like and the step of requiring a craftsman to cut carefully along said angle. A device is also needed that eliminates the step of reading a miter angle setting from a tool and setting the miter saw at such setting. However, it is clear from the above review of the art that, at the time the present invention was made, it would not have been obvious to those of ordinary skill in this art how to build a tool capable of performing this feat.